<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Sharma, Kamendra P.</style></author><author><style face="normal" font="default" size="100%">Aswal, Vinod K.</style></author><author><style face="normal" font="default" size="100%">Kumaraswamy, Guruswamy</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Adsorption of nonionic surfactant on silica nanoparticles: structure and resultant interparticle interactions</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Physical Chemistry B</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2010</style></year><pub-dates><date><style  face="normal" font="default" size="100%">SEP</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">34</style></number><publisher><style face="normal" font="default" size="100%">AMER CHEMICAL SOC</style></publisher><pub-location><style face="normal" font="default" size="100%">1155 16TH ST, NW, WASHINGTON, DC 20036 USA</style></pub-location><volume><style face="normal" font="default" size="100%">114</style></volume><pages><style face="normal" font="default" size="100%">10986-10994</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Addition of nonionic surfactant, C(12)E(9), to an aqueous dispersion of charge stabilized silica nanoparticles renders particle aggregation reversible. In contrast, aggregation of the same silica particles in aqueous solutions is irreversible. We use a combination of small-angle X-ray scattering (SAXS) and contrast matching small-angle neutron scattering (SANS) to investigate interparticle interactions and microstructure in dispersions of silica particles in aqueous nonionic surfactant solutions. We show that the silica particles interact through a screened Coulombic interaction in aqueous dispersions; interestingly, this interparticle interaction is hard-sphere-like in surfactant solutions. In surfactant solutions, we show that the final surfactant-particle structure can be modeled as 14 micelles adsorbed (on average) on the surface of each silica particle. This gives rise to the short-range interparticle repulsion that makes particle aggregation reversible, and results in the hard sphere interparticle interaction potential. Finally, we show that adsorption of polyethylene imine on the surface of the silica particles prevents adsorption of surfactant micelles on the particle surface.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">34</style></issue><custom3><style face="normal" font="default" size="100%">Foreign</style></custom3><custom4><style face="normal" font="default" size="100%">3.603</style></custom4></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Sharma, Kamendra P.</style></author><author><style face="normal" font="default" size="100%">Choudhury, Chandan Kumar</style></author><author><style face="normal" font="default" size="100%">Srivastava, Sonal</style></author><author><style face="normal" font="default" size="100%">Davis, Hilda C.</style></author><author><style face="normal" font="default" size="100%">Rajamohanan, P. R.</style></author><author><style face="normal" font="default" size="100%">Roy, Sudip</style></author><author><style face="normal" font="default" size="100%">Kumaraswamy, Guruswamy</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Assembly of polyethyleneimine in the hexagonal mesophase of nonionic surfactant: effect of pH and temperature</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Physical Chemistry B</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2011</style></year><pub-dates><date><style  face="normal" font="default" size="100%">JUL</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">29</style></number><publisher><style face="normal" font="default" size="100%">AMER CHEMICAL SOC</style></publisher><pub-location><style face="normal" font="default" size="100%">1155 16TH ST, NW, WASHINGTON, DC 20036 USA</style></pub-location><volume><style face="normal" font="default" size="100%">115</style></volume><pages><style face="normal" font="default" size="100%">9059-9069</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;We investigate the dispersion of a pH responsive polymer, polyethyleneimine, PEI, in a hexagonal (H(1)) mesophase of a nonionic surfactant, C(12)E(9), and water, at pH ranging from basic (pH = 12.8) to acidic (pH = 1). While the C(12)E(9)/H(2)O phase behavior is independent of pH, we demonstrate that, in the PEI/C(12)E(9)/H(2)O system, changing the pH influences PEI-C(12)E(9) interactions, and thus, influences the isotropic-H(1) phase transition. With decrease in pH, there is increasing protonation of the PEI chain, and consequently, the chain extends. We show, using a combination of SAXs, optical microscopy and visual experiments, that the inclusion of PEI in a 1:1 surfactant water mixture, lowers the hexagonal-isotropic transition temperature, T. At higher pH = 12.8 T(HI) shows a pronounced decrease from SO to 13 degrees C on addition of PEI, and the PEI/C(12)E(9)/H(2)O system forms a transparent gel. At pH = 1, we observe qualitatively different behavior and an opaque gel forms below T(HI)= 25 degrees C. The isotropic-H(1) transition, in turn, influences the phase separation of PEI chains from the C(12)E(9)/H(2)O system. 2D NMR ROESY data provides evidence that there are strong surfactant PEI interactions at high pH that significantly reduce at lower pH. The NMR data is in accord with molecular dynamics simulations that show that surfactants strongly aggregate with unprotonated PEI chains, but not with fully protonated chains; thus, in this system, the pH controls a cascade of microstructural organization: increasing pH decreases chain protonation and increases polymer-surfactant interactions, resulting in suppression of the isotropic-H(1) transition to lower temperatures, thus, influencing the phase separation of PEI from the surfactant/water system.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">29</style></issue><custom3><style face="normal" font="default" size="100%">&lt;p&gt;&lt;span style=&quot;color: rgb(102, 102, 102); font-family: Roboto, sans-serif; font-size: 13px;&quot;&gt;Foreign&lt;/span&gt;&lt;/p&gt;</style></custom3><custom4><style face="normal" font="default" size="100%">3.71</style></custom4></record></records></xml>